Meraki MS250 cannot communicate when plugged into a Cisco router

[DHAnderson]

I am falling back from a configuration were I was going to use a Meraki MS250 switch to replace a Cisco router. 

There is a Cisco switch plugged into the Cisco router. If the MS250 is plugged into the Cisco switch, the MS250 can communicate to the Meraki cloud and everywhere else without any issue.

If I plug the uplink of the MS250 directly into the Cisco router, no traffic flows.

The configuration of the router does not have any mac address rules, but is not providing a native VLAN on the interface descriptions.  I had a case where a MX84 would not pass traffic to a 3rd party switch until the 3rd party switch was reprogrammed to provide a native VLAN.  I am wondering if I am facing the same issue. 

I have a dump of the configuration of the Cisco router, but I do not have management access to the switch.  I thought I would bounce this off the community before asking to change the router configuration.

[TheITWay]

Hello DHAnderson, 

Probably the Native VLAN configuration is not allowing the Meraki Switch to reach out to the internet properly. 

I would go and configure the uplink port in the local status page of the Meraki switch as an access port in any VLAN (or the VLAN that is configured in the upstream router if it has one) and provide a static IP address to ensure it is not expecting any trunk negotiation and just send regular traffic as any endpoint. 

If that does not work, then you will need to configure both ports the same. Let me know if that works...

[PhilipDAth · Accepted solution]

If the router does not have a "native vlan", or rather it does not have a dot1q tag configured then it will be configured as an "access port" on the switch side.

The switch should have its port configured as an access port in whatever vlan the "main" vlan is.

[DHAnderson]

There are 2 VLANs, one for voice and another for data.

If I configure the uplink port as an access port, do I set the set data as the VLAN, and the Voice as the voice LAN?

[DHAnderson]

This morning I got a chance to try changing the Meraki uplink port from a trunk to an Access port, but that did not solve the problem.  Traffic still does not flow from the Meraki to the Cisco router.

The Cisco router has this configuration for interface 0:

!
interface GigabitEthernet0/0/1.120
description ** VLAN 120 **
encapsulation dot1Q 120
ip address 192.168.120.1 255.255.255.0
ip helper-address 192.168.0.3
!
interface GigabitEthernet0/0/1.121
description ** VLAN 121 **
encapsulation dot1Q 121
ip address 192.168.121.1 255.255.255.0
ip pim sparse-mode
ip igmp version 3
!

Is the issue I am facing that there is no dot1q native vlan specified for the interface?

[DHAnderson]

When the MS250's uplink was connected to a Cisco switch, I needed to specify a native VLAN for MS250's interface for traffic to flow.

I was assuming the Cisco router would behave in the same way, so when the MS250's uplink was connected to the router, it would need the native VLAN defined. Sadly traffic wouldn't flow.

When I removed the native VLAN from the MS250's uplink port and connect it to the Cisco router, everything started working.